The exterior surfaces of houses and other structures are often protected by exterior siding products made from wood, vinyl, aluminum, bricks, stucco, fiber-cement and other materials. Wood and fiber-cement siding (FCS) products, for example, are generally planks, panels or shakes that are attached to plywood or composite walls. Although wood siding products are popular, wood siding can become unsightly or even defective because wood generally rots, warps or cracks over time. Wood siding products are also highly flammable and subject to insect damage. FCS is an excellent alternative building material because it is nonflammable, weatherproof, relatively inexpensive to manufacture, and does not use the limited remaining cedar or fir resources. FCS also does not rot, nor is it consumed by insects.
FIG. 1 shows a prior art fiber-cement shake-panel 20 having a length L extending along a longitudinal direction and widths W1 and W2 extending along a direction transverse relative to the length L. The shake-panel 20 has side edges 23 separated from each other by the longitudinal direction, a top edge 22 extending along the longitudinal dimension between the upper ends of the side edges 23, and a bottom edge 24 extending along the longitudinal dimension between the bottom ends of the side edges 23. The top and bottom edges 22 and 24 are typically substantially parallel to each other and separated by a constant widthwise dimension or varying widthwise dimensions (e.g., W1 or W2). The shake-panel also includes a web portion 32 and a plurality of shake sections 30a and 30b of different lengths Ls1 and Ls2 projecting from the web portion 32. The individual shake sections 30a and 30b are separated by slots 28 such that the shake sections 30a and 30b have various widths corresponding to the distance between adjacent slots 28.
FIG. 2 illustrates an early prior art cutting machine 34 suitable for forming the shake-panel 20 shown in FIG. 1. Referring to FIG. 2, the cutting machine 34 includes a frame 36, a plurality of cutting stations 35a-35d, and a plurality of rollers 58 for supporting and advancing a sheet of fiber-cement to be cut. The cutting stations 35b and 35c are configured to cut the slots 28 shown in the shake panel 20 of FIG. 1. The cutting station 35b includes a slot cutting assembly 53 having a blade holder 54, a plurality of cutting blades 56 attached to the blade holder 54, and an actuator 60 for driving the blade holder 54 along rotational path R1. Each cutting blade 56 is configured to cut an individual slot 28 shown in the shake panel 20. The blade holder 54 is pivotally connected to the frame 36 such that the actuator 60 moves the blade holder 54 along the rotational path R1 between a cutting position (lowered position not shown in FIG. 2) and a retracted position (raised position shown in FIG. 2). The cutting station 35c includes a cutting assembly 63 having a blade holder 62 pivotally connected to the frame, a plurality of slot cutting blades 64 attached to the blade holder 62, and an actuator 60 coupled to the blade holder 62 and the frame 36 to rotate the cutting assembly 63 along another rotational path R2.
FIG. 3 illustrates a cutting assembly 63a used in a later cutting machine described in U.S. patent application Ser. No. 11/371,452 filed on Mar. 8, 2006, which is incorporated herein by reference in its entirety. The cutting assembly 63a includes a blade holder 62a, a plurality of cutting blades 64a attached to the blade holder 62a, and a lower anvil 70 with a plurality of slots 72 configured to receive respective cutting blades 64a. In operation, a fiber-cement workpiece (not shown) is gripped between rollers 58a and drive belts 59 that move the workpiece along a path P until the workpiece is positioned at a desired location between the cutting blades 64a and slots 72. An actuator (not shown in FIG. 3) rotates the workpiece holder 62a downwardly as indicated by arrow R so that the cutting blades 64a pass through the fiber-cement workpiece and into corresponding slots 72. The rollers 58a and/or the belts 59a then drive the workpiece along the path P to withdraw the workpiece from the cutting blade 64a, and then the actuator rotates the workpiece holder 62a upwardly into the position illustrated in FIG. 3.
PacTool International, Ltd. (PacTool), the assignee of the present invention, developed the cutting machines shown in FIGS. 2 and 3. Although the existing cutting machines illustrated in FIGS. 2 and 3 are suitable for forming the shake-panel 20 illustrated in FIG. 1, they required a significant amount of maintenance that increased the operating cost. For example, the shape of the cutting blades 64a and the rotational motion of the blade holder 62a required a significant amount of force to drive the cutting blades through the fiber-cement workpiece. This generally caused a sudden fracture in the fiber-cement workpiece that would in turn transmit significant impact forces to the lower plate 70, the blade holder 62a and the frame 36. The impact forces were so great that welded connections between members of the frame 36 cracked and broke apart, and other parts of the machine would wear quickly. Therefore, PacTool sought to improve the longevity of the cutting machine.
In addition to the high operational costs of the existing cutting machines, the fiber-cement industry is moving toward pre-painted shake-panel products in which the shake-panels are painted or stained at a manufacturing site before they are shipped to a distributor and installed. The shake-panels are painted or stained in a manner in which particles or dust remaining on the cut shake-panels can foul the paint and/or the painting equipment. This can increase maintenance costs and downtime for the painting equipment and reduce the quality of the finished coat of paint. The cutting blades 56, 64 and 64a illustrated in FIGS. 2 and 3 produce good quality edges along the slots without creating nearly as much dust as a rotating abrasive disc, but these blades nonetheless produce a small amount of dust that sticks to the shake-panels and subsequently fouls the painting equipment used to pre-paint the shake-panels. Therefore, PacTool International also sought to develop an improved cutting machine that could produce fiber-cement shake-panels suitable for pre-painting operations.